Secure Digital (SD™) refers to a standard maintained by the SD Association covering nonvolatile memory card technology. SD cards are used primarily in portable devices (known as “hosts”) such as mobile phones, Global Positioning System (GPS) navigation devices, and digital cameras. The SD standard describes four performance-based families: SD Standard Capacity (SDSC™), SD High Capacity (SDHC™), SD eXtended-Capacity (SDXC™) and SD Input Output (SDIO™). The SD standard also describes three form factors of increasingly smaller size: SD, miniSD™, and microSD™. Electrically passive adapters allow a smaller card to fit and function in a device built for a larger card.
Cards in the SCSC, SDHC, and SDXC families are used as regular memory cards and offer increased capacity progressing through -SC to -HC to -XC. Cards in the SDIO family can provide input/output functionality, such as geolocation, radio and television reception, barcode reading, and external interfaces such as Wi-Fi and IrDA when the card is inserted into a host.
FIG. 1 presents two outline views of the form factor of a microSD card 100—a top perspective view 110, and a bottom perspective view 120 (rotated 180 degrees away from the viewer about the long axis of the top perspective view 110). The overall dimensions of the microSD card are 15 mm long, by 11 mm wide, by 1 mm thick. Asymmetrical profiles on the long sides of the microSD card prevent inserting it in a host microSD slot upside down.
A thumb ridge 112 forms an arc concave to a first short side, in part to assist in removal of the card 100 from a host. Conductive electrical contacts 132 are exposed in the bottom view 120 proximate the second short side for electrical interface (both data communication and power) with a host. The notch 114 formed in one of the long sides interfaces with a corresponding retention device in the host to physically secure the card during operation.
Traditional thermoset plastic overmolding involves molding one thermoplastic material over another to form a single part. Traditional packaging of electronics includes a printed circuit board assembly containing passive and active elements, along with interface components inside a clamshell housing. A form of overmolding can be applied to electronics packages, eliminating the need for the clamshell housing. After creating a PCB assembly (PCBA), the PCBA can be inserted into a mold, and injected thermoset plastic can surround the PCBA. Properties of the thermoset plastic are chosen for various reasons, including to prevent inadvertent interactions with any of the materials being molded over, and to under fill electrical components such as flip chip devices. This approach can provide mechanical and moisture protection, vibration resistance; and also can reduce the number of manufacturing steps.